RF TEST RESULT OF A BNL N-DOPED 500 MHz B-CELL CAVITY AT CORNELL*

Cornell’s SRF group has collaborated with Brookhaven National Laboratory (BNL) on one 500 MHz CESR type SRF “B-cell” cavity (BNL B-cell) for the National Synchrotron Light Source II. Cornell has been responsible for RF surface preparation, vertical testing, and short cavity string assembly. As a state-of-the-art surface preparation protocol, Cornell selected “Nitrogen doping” for the BNL B-cell. N-doping has been well demonstrated and established to push the cavity quality factor (Q0) higher in 1.3 GHz SRF cavities at many laboratories. Cornell calculated that N-doping could also be beneficial on a 500 MHz SRF cavity, with a potential to increase its Q0 by a factor of two compared with the traditional chemical polishing based surface preparation protocol. Here we report on the detailed surface preparation and vertical test result of the BNL B-cell.